The present invention relates to a method and a device for stopping a vehicle at a predetermined position and particularly to a method and a device which makes it possible to stop a vehicle, which is driven by discrete control commands generated for example by notching representing predetermined brake settings, at a predetermined target position with high accuracy and with less changes in notching operation.
FIG. 1 is a block diagram illustrating an example of a conventional device for automatically stopping a train at a predetermined position and FIG. 2 is a graph illustrating a velocity pattern for explaining the operations thereof. In FIG. 1, the device comprises a tachometer generator 1, a velocity calculating circuit 2, a distance integrating circuit 3, a position marker 4, a point signal detector 5, a pattern generator 6, a comparator 7, a brake controller 8 and a brake device 9.
According to this conventional device, the point signal detector 5 disposed on a vehicle detects the position marker 4 provided on the ground at a position P (hereinafter referred to as point-P) a predetermined distance l on this side of a target position O (hereinafter referred to as point-O). In response to a point detection signal from the point signal detector 5, the distance integrating circuit 3 counts pulses from the tachometer generator 1 so as to produce a distance S along which the vehicle has travelled from the point-P to the current position at that time, and the pattern generator 6 selects a value of the distance l to the target position out of a memory provided therein so as to produce a target velocity pattern V.sub.P on the basis of the following equation (1): ##EQU1## where .beta..sub.P represents a predetermined deceleration.
The tachometer generator 1 produces pulses at a frequency proportional to the current vehicle velocity V.sub.T and the velocity calculating circuit 2 calculates a digital value of the current or actual velocity V.sub.T of the vehicle from the pulses. The comparator 7 compares the current or actual velocity V.sub.T with the target velocity pattern V.sub.P produced from the pattern generator 6. On the basis of an output (V.sub.T -V.sub.P) of the comparator 7, the brake device 9 is proportionally controlled by the brake controller 8 so that the current or actual velocity V.sub.T follows the target velocity pattern V.sub.P to stop the vehicle in close vicinity to the target point-O.
In this conventional device, however, there may occur an offset of tracing error with respect to the target velocity pattern V.sub.P due to the deviations in brake force of the brake device 9 as well as the deviations in external force due to the grade of railway, thereby deteriorating the stop gap accuracy. Further, if integral control is performed for the brake device 9 in addition to the proportional control in order to prevent the above-mentioned offset of tracing error from occurring, it will necessarily increase the frequency of notch-changings, i.e., change of brake settings, to cause another problem that a ride in the vehicle may become uncomfortable.